Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Users might experience few discrepancies in Search results. We are working on this on our side. We apologize for the inconvenience it may have caused.
New Member

Voice QoS/CoS in Ethernet

The CIPT course material says that Cisco IP phones use the 802.1p field in the 802.1Q tag to classify voice packets with a CoS value of 5. What happens to the 802.1p field if we have ISL trunks between switches? Or do we have to run 802.1Q trunks in order to preserve the CoS bits?

1 REPLY
New Member

Re: Voice QoS/CoS in Ethernet

You are correct. You will need to run .q trunks to preserve the COS. I have heard of some people using the other mechnisms to repaint the packet when crossing ISL trunks (like using the PFC in a 6000)

176
Views
0
Helpful
1
Replies
CreatePlease to create content